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a genus of herbaceous plants of the papilionaceous family (Leguminosae).
The leaves of Arachis are compound even-pinnate. Some species have cleistogamous as well as chasmogamous flowers from which the underground fruit are formed. After fertilization the ovary is buried in the ground by the gynophore (an elongated flower receptacle) that grows from its base. There are 15 species of Arachis in South America. Their ecologies differ: some species grow in forest clearings and at the edge of the forest; others grow on the floodplains of rivers; and still others grow in hot, arid places in sandy soil.
Cultivated Arachis—also called the groundnut, peanut, Chinese nut, and Chinese pistachio (A. hypogaea, 2n = 40)—an annual plant 25–75 cm tall, is widely grown as a crop. The Arachis shrub is either upright or creeping, and the flowers are yellow or yellow orange, papilionaceous, cleistogamous and chasmogamous, and gathered in clusters. The mature pod has one to seven seeds and a fragile, strawlike shell; each seed has a red, dark brown, or light brown covering. The species A. hypogaea is divided into three subspecies: the South American (ssp. australia-americana), the Asian (ssp. asiatica), and the common (ssp. vulgaris), which are cultivated in the tropical, subtropical, and temperate zones of Asia, Africa, America, Australia, and Europe, where there is sufficient moisture. The best soils for cultivating Arachis are rich, with light texture. In the USSR only the common peanut is cultivated.
In the 16th century the cultivated Arachis was introduced into Asia from South America, and then into Europe from China. Arachis was brought into Russia at the end of the 18th century, but it began to be grown in fields only in the Soviet period.
The seeds of Arachis contain a high-quality fatty oil which is used in canning, in the making of margarine and soap, and in other branches of industry. Fruit that are 10 percent moisture contain about 42 percent oil, up to 22 percent protein, and about 13 percent carbohydrates. Confectioneries are made from the seeds of Arachis; roasted seeds are used for food. The vegetable pulp of the plant is used for cattle feed.
Arachis crops occupy over 16 million hectares (1964). The gross yield of fruit is about 14 million m, and the average harvest is nine centners per hectare. The largest cultivated areas are in India, China, Burma, Indonesia, African countries, and the USA.
In the USSR, Arachis is grown in Middle Asia, Transcaucasia, the Ukraine, and Krasnodar Krai. On the most advanced farms the yield is as much as 40 centners per hectare when the crop has been irrigated; without irrigation, the yield is 10–16 centners per hectare. There are regional varieties of Arachis, such as Perzuvan 46/2, Zakataly 294/1, Krasnodar 1708, and others. The methods of cultivating Arachis are the usual ones for tilled crops. The most important fertilizers are those containing phosphorus and nitrogen. Arachis seeds or pods are sown in warm (up to 14–15°C), moist soil, in squares (measuring 70 x 70 cm, with seven to eight seeds or four to five pods in a hill) or in wide rows at a depth of 6–10 cm. The standard quantity of seed used is 50–90 kg per hectare; 30 percent more pods than seeds are used per hectare. After the field has been sown, it is rolled. Care after sowing includes cultivation between the rows of plants, weeding the hills and rows, hilling the plants when they flower, and irrigation (up to eight times) when conditions require it. Herbicides (atrazine, monuron, 2,4-D, and prometrine) are effective when applied before germination. Arachis is harvested with a peanut-harvesting machine. The seeds are treated with granoz or thiuram with a gamma isomer, and the plantings are treated with ground sulfur (to protect against red spider mites).
REFERENCESLuzina, Z. A. Arakhis. Moscow-Leningrad, 1954.
Onuchak, A. I., and G. A. Ezernitskii. Arakhis. Moscow, 1954.
Rukovodstvo po selektsii i semenovodstvu maslichnykh kul’tur. Moscow, 1967.
D. T. UMEN and V. N. VEKHOV